1. Field of the Invention
The present invention relates generally to easy open ends for containers, and in particular relates to easy open metal ends which employ a "moustache" vent score.
The term "easy open end" is used generally for that class of ends for containers which are provided with a mechanism for permitting the consumer to open the container at the end for access to the ingredients within the container, without the use of a can opener or other machinery. One conventional easy open end technique employs a pull tab having a pointed nose, the pull tab being riveted to the panel of the end so that the nose rests adjacent a weakened area along the periphery of the end panel. To open, the pull tab is rotated about the rivet, causing the nose to fracture the weakened area. Further pulling of the tab away from the end panel then causes the remainder of the weakened peripheral to rupture, thereby permitting the entire end to be opened.
It is also known in the prior art to employ a vent score behind the rivet toward the center of the panel to relieve internal pressure within the container, and thereby avoid implosion or explosion as the container is opened by rotation of the pull tab about the rivet. The most frequently used shape for the vent score is curved much like a man's moustache, and is therefore conventionally referred to as the "moustache score". FIGS. 1 and 2 illustrate prior art moustache score techniques, as is described further below.
Noting FIG. 1, a prior art end panel employing a moustache score is referred to generally by the reference numeral 10. Typically, the end panel is formed of tin-plated stainless steel, and includes a peripheral bead 14 which is conventionally attached to the end of either a metal or composite container. The end panel further includes a peripheral weakened area 16, which may be formed by crimping, scoring or other means. The central area of the end is an essentially flat metal area. A pull tab 18 (which is shown in dotted lines to illustrate the appearance of the moustache score 28, described in greater detail below) is joined to the central area 12 via a rivet 20. The pull tab 18 includes lateral and opposing sides 24, 26 which extend forwardly to a pointed nose 22, and which rests adjacent and over the weakened area 16. The moustache score 28 includes a pair of outward curves 30 and an inward curve 29, the inward curve essentially curving about the rivet in the direction of the center of the panel 12. Conventionally, the apex of the outer curves 30 lie within the area bounded by the sides 24, 26 of the pull tab 18.
It is also conventional to employ a peripheral reinforcing bead 32 spaced inwardly from the weakened area 16, and a pair of lateral reinforcing beads 34, 36 which extend across the central area 12 of the end panel 10. As thus configured, the prior art end panel 10 defines an area 15 generally between the rivet and the weakened area 16, and a thin portion between the rivet 20 and the inward curvature 29 of the moustache score 28.
A major disadvantage of an end panel like that described above with reference to FIG. 1 will now be described with reference to FIG. 2. As is shown in FIG. 2, the pull tab is used to open the container by pulling upwardly about the rivet 20, causing the nose 22 to rupture the weakened area 16. It is frequently necessary to rotate the pull tab virtually 180 degrees from its initial position in order to obtain complete rupture. When this occurs, the central area 12 of the end panel 10 is curved downwardly as is shown along portions 11 adjacent the pull tab. It has been observed that frequently the metal area 15 which lies between the rivet 20 and the weakened area 16 tears along line's 38 and 40, thereby creating a dangerous cutting edge which may injure the consumer.